Zoom on, you blue devil...
Nothing much has changed from the first Advance title. You pick from one of 5 characters (Sonic is only available at first, and Amy must be unlocked through various means....), and race through a stage. Characters have their arsenal of abilities changed from Advance, and new "trick" abilities have been added (they're just for show or reaching ledges, though). Newcomer Cream joins the fray, bringing along flight (like Tails, but different) and a partner Chao that can home in on and attack enemies. Way to make the game easy with her, Sega.... The speed from Advance has definitely been increased, so one shouldn't feel that this Sonic is "slow". But perhaps, the game's greatest strength is its greatest weakness. With all of the focus on the speed, it seems that the developers threw exploration out of the window. In fact, in order to find specific items, such as special rings that you need in order to enter Special Stages, you need to go out of your way... And given some of the level design, that simply isn't an option. Maybe it's just me, but the difficulty does seem to ramp up pretty quickly in the game.
Music: It's Sonic. There's always good music. Sure, some of the Act-to-Act remixes are kinda weird (see Ice Paradise), but other times they add on to the exhilarating feel of the Zones (see Music Plant, Leaf Forest, or pretty much any other Zone).
The graphics are the same as Advance (nor did they get any better in 3), but that's not a problem. My one complaint: make the Zone backgrounds more detailed.
All in all, its a good game. One should find themselves plugging into this game a solid amount of time with the 5 characters and various unlockables. If you can't find any of the Rush series, or Advance 3, pick this game up. You won't be disappointed.